Techniques and sensors for detecting molecules and specific substances such as peptides, enzymes, antigens, antibodies, oligonucleotides, DNA or RNA fragments in a sample solution are known in the art. In a specific class of sensors, use is made of the principle of measuring the impedance between two electrodes. The absence or presence of oligonucleotides, peptides/proteins, or antigens between the electrodes affects the permittivity and/or the conductivity between the electrodes.
As lithography and e-beam patterning are expensive, a new cost-effective approach was proposed in EP 0 876 601. An insulating substrate is patterned with a plurality of interspaced channels with submicron dimensions. Hills are located on this insulating substrate near the channels such that shadow zones are obtained upon non-orthogonal directional deposition of a conductive material thereby forming an impedimetric device. In J. Micromech. Microeng. 10 (2000), N1-N5, P. Van Gerwen et al propose an optimised design for this sensor, i.e. the hills are located at the end of the channels forming a shadow zone reaching part of the subsequent channel. This avoids electrical contact between adjacent electrode fingers and ensures the formation of interdigitated electrodes.
In EP 0 876 601 and J. Micromech. Microeng. 10 (2000), N1-N5, a sensor comprising interdigitated electrodes on an insulating substrate is described as well as a method for producing this sensor without lithography. To detect the presence or absence of molecules, the change of the impedance between interdigitated electrodes is measured. To increase the sensitivity various single sensors may be combined, possibly containing different probes for binding to different molecules. The different electrodes of these sensors are electrically isolated by microelectronics patterning techniques. This results in extra processing steps including expensive lithography.